Earthmoving and construction vehicles utilize many mount assemblies that require relative angular rotation between the elements thereof and high operating loads. In the past, these assemblies have been primarily mechanical joints that have to be lubricated or used without lubrication. Naturally, rotatable joints without lubrication will wear more quickly, especially when subject to heavy workloads. In the past, there have been various efforts to provide a resilient joint assembly having relative rotation between the elements thereof while the assembly is being subjected to heavy workloads. In these attempts, it has been necessary to preload the elastomeric material in order to achieve the needed life of the assembly. Furthermore, in order to withstand heavy loads, the thickness of the elastomeric material has been kept as thin as possible. However, when keeping the elastomeric material thin, the ability to rotate the members relative to each other is seriously handicapped, since large amounts of angular rotation results in rupturing of the elastomeric material. Consequently, in order to get high relative rotation between the elements, the thickness of the elastomeric material must be increased. As previously noted, to withstand heavy loads, the elastomeric material should be thin. Therefore, in order to obtain high angular rotation between the elements while working under heavy loads, it has been necessary to provide numerous layers of thin elastomeric material, each being separated by a metallic member. In these arrangements, it becomes extremely difficult to preload the assembly and obtain an even, uniform preloading of the elastomeric material.
The characteristics of mechanisms using preloaded rubber is set forth in an article entitled "Dynamic Fatigue Life of Rubber" by S. M. Cadwell. This article was taken from the Analytic Edition, Volume 12, pages 19-23, of the "Industrial and Engineering Chemistry" book, dated Jan. 15, 1940. This article teaches the basic principle that the ability of a rubber material to withstand rupture due to shear forces is increased substantially if the rubber material is placed under a compressive load. From a review of the subject article, it should be recognized that when a rubber material undergoes internal movement, the rubber material is undergoing a shear deformation. This shear deformation can continue for numerous cycles without rupturing of the rubber material. The fatigue life of the rubber material during shear deformation is greatly enhanced by having the rubber material subjected to a compressive load.
U.S. Pat. No. 3,504,905 issued Apr. 7, 1970 to A. S. Irwin and U.S. Pat. No. 3,989,126 issued Nov. 2, 1976 to E. Katzer, each teach resilient mount assemblies that allow large amounts of rotation between the elements without rupturing of the elastomeric material, but are limited in their abilities to withstand high operating loads.
U.S. Pat. No. 3,494,814 issued Feb. 10, 1970 to R. L. Boggs teaches a resilient mount assembly designed to handle heavy operating loads while also having the ability to have high angular rotation between the elements without rupturing of the elastomeric material. In order to provide the high angular rotation between the elements, the assembly has numerous individual pieces bonded together by a very thin elastomeric material and then preloaded by forcing the assembly into a circular ring. Even though this arrangement provides a resilient mount assembly that can withstand high loads and provide high angular rotation between the elements, it is an extremely complicated mechanism to build and assemble and in many applications would be extremely difficult to uniformly preload the elastomeric material.
U.S. Pat. No. 4,111,499 issued Sept. 5, 1978 to A. R. McCloskey teaches a bearing assembly. As shown in FIGS. 4 and 5 thereof, the bearing assembly has a liner material and a coat of resin separated by a backing material. The liner and backing material is formed between two members to provide a moveable bearing assembly. In this arrangement, there is no shear deformation in the liner material or the coat of resin.
U.S. Pat. No. 4,690,231 issued Sept. 1, 1987 to P. Riml and U.S. Pat. No. 4,772,151 issued Sept. 20, 1988 to B. G. Lammers, et al., each teach a resilient mounting assembly. The elastomeric material of the mounting assembly is preloaded to obtain a mount that can withstand heavy operating loads, but the degree of rotation between the elements is limited to a few degrees.
The present invention is directed to overcoming one or more of the problems as set forth above.